Loose and slutty always works for attention with guys; but...he'll likely not call you back the morning thereafter. Most guys like to see something tight on your butt, i.e., classy body hugging denims, with high heels and that come hither look. Don't date someone shorter than you though, otherwise you'll get that Tom Cruise silly look, you know, the kind where he has to wear elevator shoes to look normal with Katie. Oh shoot, that one's over now! But don't wear all that if you're not planning on hot passion, or a kid in your future.
This varies from guy to guy. If there's a certain kind of style you like in guys, mirror that with the girl's version, and you'll probably get the attention of guys with that style. Makes sense to me, anyways. Whatever you wear, be comfortable and confident. If you aren't, you're not wearing the right clothes.
Nothing too outlandish. Jeans, skirts, leggings, short shorts are all fine. Nothing too manly. I don't like lots of brand names to be visible, but a small logo or hidden logo of a high quality brand are good.